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AUTHOR: hanna · Updated: 6th Jan 2022

The Best Online Casinos for Slots in the US

Compared to other casino games found at US casino sites, slot machines are a relatively new invention. The world’s first one-armed bandit arrived in San Francisco in 1894, with three reels, one payline, and playing cards used as the game’s symbols. Today, online slots come in a variety of forms, but the formula remains much the same: spin the reels and hope for the best!

Welcome to GamblingDeals’ roundup of the best slots casinos. As with all of our pages, we’ve worked hard to supply our users with trustworthy information on all the top sites. Our expert reviews are unbiased, and our leaderboards make it easy for prospective players to compare welcome bonuses and other unique site features. Let’s jump right in. 

The Different Types of Slots

Slot games have been the most dominant gaming category at online casinos for many years. There are thousands of titles that loosely fit under the ‘slot game’ umbrella, but there are four main sub-categories – classic, video, progressive jackpot, and Megaways. Whichever type players favor comes down to a matter of personal preference, but here’s what you can expect from each: 

Classic Slots

So-called because of their deliberate resemblance to mechanical slots of the past, classic slots are small on features and big on character. Like the machines of the 19th century, these games often just have the minimum three reels, often filled with iconic fruit symbols, and usually fewer paylines – just the one in many cases. 

Although these games are arguably less thrilling than iterations of slots that have come since, many players enjoy the nostalgic nod to the past and the simple gameplay of classic titles. Elk Studios’ Route 777 and Mega Joker from NetEnt are two popular examples for fans of the old-school. 

Video Slots

The majority of games at a US slot casino will be made up of video slots. These titles can be distinguished from classic variants by their superior graphics, animated gameplay, immersive bonus features, and an increase in both the number of reels and paylines.

All these elements combine to produce a more fast-paced, high-octane game, where players will be able to utilize free spins, multipliers, and other exciting features. There are simply too many video slots to mention, but two of the biggest titles of the last decade have been Gonzo’s Quest from NetEnt and Book of Dead from Play’n Go. 

Progressive Jackpot Slots

You might have heard tales of $0.25 wagers returning millions of dollars to some lucky online casino players, and that’s exactly what can happen with progressive jackpot slots. As the name suggests, players of these games contribute to a rolling jackpot, regardless of what casino site they’re using to play. Jackpots build steadily before suddenly being won by one lucky player. Be careful though – these games often have lower payout rates than other slots, and the chances of landing the top prize are akin to winning the lottery. 

Microgaming’s millionaire-maker Mega Moolah is an abiding game of the genre, as is NetEnt’s Mega Fortune. 

Megaways Slots

In 2016, Big Time Gaming (BTG) engendered a new dawn of online slots with the introduction of its Megaways payline structure. The number of paylines in a Megaways slot is fluid, ranging from hundreds to 117,649 ways to win. While the other slots we’ve mentioned have a fixed number of symbols on their reels, Megaways slots change with every spin – there can be a maximum of seven symbols on each reel or as few as two. 

This generates fluctuations in the number of active paylines, which can lead to some interesting combinations. Buffalo Rising Megaways from BTG and Blueprint Gaming’s Fishin’ Frenzy Megaways are two of the biggest slots in this category. 

How to Win at Slots

No matter which slot you’re playing, the aim is to match winning combinations of symbols on the reels. Traditionally, these combinations must be in sequence from left to right, but some titles have a win-both-ways payline structure. If you do manage to land a winning combo, your prize will be paid out according to both the value of the symbols involved, and the size of your stake; the bigger the wager, and the more valuable the symbols, the higher the payout. 

Beyond these basics, here are some other important factors to making a success of the slots:


A payline is the designated route to victory on an online slot. As we mentioned above, classic slots may only have one payline, while Megaways titles can have hundreds of thousands. Most slot games will have between five and 20 paylines, but pay attention to whether these are fixed or variable – if they’re fixed, all paylines will be active; if they’re variable, players can decide how many they want to have in play. As you pay per payline, a smaller number will cost less, but also reduce your chances of a netting winning combination. 

Some modern slots use a Cluster Pays mechanic. Originated by NetEnt, this game type does away with classic paylines and instead rewards players for landing clusters of matching symbols adjacent to each other. While this looks different, the logic is the same. The more symbols in a cluster, and the higher their value, the more you win. 

Bonus Rounds

Modern online slots are packed full of bonus rounds, offering players more interesting gameplay and additional chances to win real money prizes. The most common features are free spins rounds, unlocked by landing certain combinations on the reels – usually scatter symbols. The action of these bonus rounds often takes place in a different setting to the base game, providing an opportunity for slot developers to show off their flair for game design. 


Many online slots also use multipliers as a means of generating bigger wins for players; when this feature is in play, winnings can be doubled, tripled, quadrupled, or more. Multipliers can be attached to free spins rounds, activated by consecutive wins, or triggered at random. 


Gonzo’s Quest is the typical example of an avalanche slot. Also known as cascading reels, after every winning combination, the tiles that were used to form a winning combination will tumble away and be replaced by new symbols. 

If the addition of these new symbols forms another winning payline, the avalanche feature will be reset. Avalanche reels allow players to continue their run of luck without having to place a wager on another spin, and are often used in conjunction with multipliers.

Online Casinos Slots Bonuses and Offers

The best slots casinos will offer their members a sequence of bonuses and promotions throughout their time at the site. This kicks off with a generous welcome bonus, followed up by smaller, more targeted offers on a consistent basis. 

Before making use of any slots casino offers, make sure you always read the small print, as terms and conditions will usually apply. 

Free Spins Bonuses

You’re here to play at the top US slots casinos, so you’ll be wanting to know about free spins bonuses. These can either be issued as part of a welcome deal, or as an exchange for a minimum deposit into a player’s casino account. 

Free spins bonuses are often targeted at a specific title, such as 20 free spins on Play’n Go’s Rich Wilde and the Book of Dead. 

Matched Deposit Bonuses

Another regular welcome offer, matched deposits see players receive a portion of their first deposit at the casino’s expense. For example, if you were to make use of a 100% up to $100 offer, any deposit you make – within that maximum – will be met in full, doubling your bonus balance. 

No Deposit Bonuses

No deposit bonuses will credit a player’s account with either bonus cash or free spins, without the need to make a deposit. 

These bonuses tend to become active as soon as a new player registers an account at a casino site. Since no deposit offers don’t demand any financial commitment from players, amounts will be smaller than other bonuses and will normally have steep wagering requirements attached. 

RTP and Variance

No matter the style, design or bonus features of a slot game, all of them are bound by two distinct mechanisms: return to player (RTP) percentages, and variance. We’ve explained these two terms and the differences between them below:


RTP percentages are calculated when game developers run their products through millions of simulations. With each spin of the reels, the size of the slot’s payouts are recorded, aggregating the data to create an average payout that players can expect to receive over an extended period of time. The average RTP for slots is around 96%, meaning hypothetically, the machine pays out $96 for every $100 wagered on it. 

A word of warning: since these figures are generated by huge data sets, the actual return-to-player percentage can deviate massively from the advertized number. After all, if every online gambler knew precisely what they’d win from a spin of the reels, where would the fun be? 


Also known as volatility, a slot’s variance is what makes the game worth playing. Variance is an indication of the size and frequency of payouts when they arrive. If a slot has low variance, this means that real money prizes are small but frequent; if a slot has high variance, you might have to wait a while for a payout, but it could be much larger when it comes. 

High rollers will be able to afford the wait between wins on a high variance slot, but for those on tighter budgets, we advise sticking with low variance games.

Popular Slots Developers

Online casino games are provided by a rich network of software developers, all competing for players’ affections. The best slots casinos will offer titles from a range of developers, here are some of the biggest names to look out for – some of which we’ve already mentioned:


Microgaming’s products include both the world’s first online and mobile casino software, so it’s no surprise that this developer is considered one of the biggest in the industry. Founded in 1994, Microgaming’s games are varied; as well as the hits we’ve discussed on this page, slots worth checking out include Immortal Romance and Thunderstruck II.


Now owned by live dealer giant Evolution Gaming, NetEnt is considered one of Microgaming’s major rivals. Founded back in 1996, NetEnt slots can often be characterized by their highly visual graphics and detailed character animations, which combine to produce stunning games. Among the provider’s most memorable slots are Dead or Alive II and Jack and the Beanstalk. 


Playtech’s influence on the online gambling industry is just as significant as the two developers above. Indeed, these three developers are often referred to as the industry’s ‘Big 3’, having all been around since the burgeoning days of online gaming. 

Playtech is perhaps best known for signing exclusive rights deals with big production studios, leading to the creation of popular slots such as The Green Lantern, The Matrix, and Gladiator. 


Founded in 2013, Yggdrasil is comfortably the youngest developer on this list, but this multi-award-winning Swedish studio packs a punch as big as any other. Inspired by the Norse mythological concept of the same name, Yggdrasil slots are best known for their creative design, strong themes, and bold color schemes – Valley of the Gods and Vikings Go Berzerk are two good examples of the developer’s impressive abilities.  

Find the Best US Online Casino for Slots

We know how difficult it can be to find your ideal online casino, which is why we work tirelessly to streamline this process for you. Our expert guides, detailed reviews, and site comparison tools make it easy for you to find and play at one of the best US slots casinos. 

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